Feed accounts for on average 35-60% of the operating costs of salmon farms and it represents the largest cost in the culture of other carnivorous aquatic species. Moreover, the protein sources presently used account for the majority of the feed cost. Accordingly, salmon farming profitability is marginal in many regions. Hence, there is a need to reduce production costs and improve the market value of the farmed product.
Currently, aquatic feeds contain high levels of fish meal and oil, which are mostly imported, to produce a protein-rich and sometimes lipid-rich (e.g. salmon diets) aquatic feed. However, as noted hereinabove, such fish meal and oil can be very expensive and this will be especially true in the future due to progressively increasing demands that are being placed on the finite global supplies of fish meal and oil. Hence, alternative economical sources of protein and lipid are required.
One known approach is to use less expensive plant protein sources in aquafeed that have been specially processed so that they are in the form of nutritionally upgraded protein meals, concentrates, and isolates. These may be used either singly or in combination with rendered animal protein ingredients such as poultry-by-product meal. To date, each of these protein products, such as canola meal, soybean meal, and poultry-by-product meal have been processed (produced) separately and then these protein sources have been blended together in dried and finely ground form in appropriate ratios for a particular aquatic species at the time of diet formulation and preparation.
Most research on oilseeds has focussed on the use of products derived from processing soybeans, rapeseed/canola, sunflower seed or cottonseed. Comparatively few of these studies, however, have been directed to assessing the feasibility of using canola, flax seed, mustard seed, hemp and the like. Indeed, in the case of canola for example, although proteins contained therein are rich in lysine and methionine, both of which are limiting amino acids in most cereal and oilseed proteins, its use as a protein source in food products has been severely limited, due to the fact that the proteinaceous material which is left over after oil is extracted by known processes contains antinutritional constituents. The latter include insoluble and soluble fibres, glucosinolates (antithyroid compounds), phenolic compounds and phytic acid.
It has been shown that the concentrations of the above mentioned unwanted constituents should be minimized in order to allow full expression of the high quality of oilseed protein and to improve the overall digestibility, palatability, as well as bioavailability of minerals in the oilseed protein product. This is highly desirable when feeding either terrestrial species or aquatic species.
U.S. Pat. No. 4,418,086 to Marino et al. discloses the preparation of an animal feed which comprises (a) a proteinaceous matrix, (b) fat or oil, (c) a sulfur source, (d) farinaceous material, (e) a plasticizer and (f) water. The method disclosed involves the blending of the ingredients together, introducing the mixture into an extruder and subjecting it to shear forces, mechanical work, heat and pressure such that the product temperature prior to discharge is at least 280 degrees F. This patent is concerned with the production of an animal feed with a “meat like texture”.
U.S. Pat. No. 3,952,115 to Damico et al. relates to a feed where an amino acid is utilized as an additive to fortify a proteinaceous feed.
U.S. Pat. No. 4,973,490 to Holmes discloses the production of animal feed products utilizing rape seed in combination with another plant species.
U.S. Pat. No. 5,773,051 to Kim relates to a process for manufacturing a fish feed which refloats after initially sinking. This document discloses a process including blending conventional fish feed containing fish meal, wheat meal, soybean meal and other substances and compressing the mixture at a constant temperature to produce a molded product.
Furthermore, U.S. Pat. No. 4,233,210 to Koch and U.S. Pat. No. 4,889,921 to Diosady et al. disclose preparations of protein concentrates for use in animal or human nourishment, from oilseeds including rapeseed (canola). The various processes of these inventions generally comprise heating, drying and distillation steps, as well as treatments with alkaline solutions and extractions with organic solvents.
The protein extract claimed by Cameron et al. in U.S. Pat. Nos. 4,418,013 and 4,366,097; and by Murray et al. in U.S. Pat. Nos. 5,844,086 and 6,005,076 is said to be “protein isolate”, which is regarded as being different from a protein concentrate. Indeed, it is established that a protein extract is an isolate when the protein content exceeds 90% and the protein is undenatured. Accordingly, the process of the preparation of an isolate does not allow for a heating step at elevated temperature.
Lawhon et al. in U.S. Pat. No. 5,086,166 disclose a process allowing for the simultaneous preparation of protein as precipitate or curd, and oil for use as food products or food ingredients, from numerous oilseeds including soybeans, glandless, cottonseeds, sunflower seeds, peanuts and sesame seeds. At an early step of the process, a heating treatment (at about 60° C. to 90° C.) of the material in water is performed, in order to inactivate enzymes inherent in the seed.
A process for the preparation of rapeseed and canola protein concentrates known as the “FRI-71 process” has been described by Jones (J. Amer. Oil Chem. Soc. 56, 1979, 716-721). This process allows for the production of highly digestible protein concentrates with reduced levels of antinutritional factors (except for phytic acid) that can be used to entirely replace the fish meal portion of diets for trout. However, subsequent work conducted in collaboration with the POS Pilot Plant Corporation in Saskatoon revealed that the FRI-71 process was not cost effective, due to low yields of the concentrates, and insufficient numbers of other value-added products apart from canola oil stemming from the process. Also, the process as described could not easily be applied in the private sector using existing oilseed and fish meal processing technology.
In the present invention, a modified FRI-71 process is described that results, besides the high value canola protein concentrate and animal feed grade canola oil, in other value-added products such as canola oil suitable for the organic food market, nutritionally upgraded canola meal, and products suitable as components in organic or predominately organic fertilizers. The process of the invention is simple and economical. Moreover, the process is readily integrated into existing oilseed crushing plants or fish meal production plants.
The process described in an embodiment of the present invention is further extended to various oilseeds including canola, rapeseed, sunflower seed, flax seed, mustard seed, cottonseed, hemp and soybeans. Moreover, mixtures of different oilseeds are also used in the process.
An object of the invention for certain embodiments is to provide an improved process for extracting protein and oil (human and animal feed grade) from oilseed. A further object of other embodiments is to provide protein products that are particularly well suited for use in high energy (lipid) diets for fish farming and in some animal feeds.